Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H19/00—Coated paper; Coating material
  • D21H19/36—Coatings with pigments
  • D21H19/38—Coatings with pigments characterised by the pigments
  • D21H19/385—Oxides, hydroxides or carbonates
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
  • C01F11/00—Compounds of calcium, strontium, or barium
  • C01F11/18—Carbonates
  • C01F11/182—Preparation of calcium carbonate by carbonation of aqueous solutions and characterised by an additive other than CaCO3-seeds
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
  • C01F11/00—Compounds of calcium, strontium, or barium
  • C01F11/18—Carbonates
  • C01F11/185—After-treatment, e.g. grinding, purification, conversion of crystal morphology
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
  • D21H17/63—Inorganic compounds
  • D21H17/67—Water-insoluble compounds, e.g. fillers, pigments
  • D21H17/675—Oxides, hydroxides or carbonates
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H21/00—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties
  • D21H21/50—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties characterised by form
  • D21H21/52—Additives of definite length or shape
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2004/00—Particle morphology
  • C01P2004/30—Particle morphology extending in three dimensions
  • C01P2004/32—Spheres
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2004/00—Particle morphology
  • C01P2004/30—Particle morphology extending in three dimensions
  • C01P2004/40—Particle morphology extending in three dimensions prism-like
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2004/00—Particle morphology
  • C01P2004/60—Particles characterised by their size
  • C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2004/00—Particle morphology
  • C01P2004/90—Other morphology not specified above

Definitions

• This invention relates to novel precipitated calcium carbonate particles of varying size and shape, and to methods for their preparation involving the use of basic calcium carbonate as a precursor.
• Calcium carbonate particles of varying sizes and shapes are useful as fillers or as reinforcing materials for rubber, paper, plastics, paints and other materials. These particles, may be roughly divided into two groups, to wit: natural calcium carbonate particles and precipitated calcium carbonate particles. Natural calcium carbonate is prepared by mechanically grinding limestone to particle sizes as small as 0.5 microns, although it becomes increasingly difficult to grind limestone below one micron. Moreover, ground limestone particles are usually very irregular in shape, and ordinarily exhibit a broad particle size distribution.
• Size control by varying slake and carbonation conditions is generally related closely to the resultant morphology and is usually limited to a relatively narrow range for each type of product.
• Morphology and size are also significantly influenced by addition of various additives to slaked lime before carbonation. This is illustrated by U.S. Patent 4,714,603 in which a synthesis for the preparation of spherical calcite particles is described wherein a dissolved polyphosphate is added to slaked lime prior to the introduction of carbon dioxide. Particle sizes of between 2.5 and 10.0 microns are disclosed with the size depending upon the quantity of polyphosphate added.
• the synthesis appearing therein comprises preparing a slurry of calcium hydroxide by hydrating calcium oxide at a temperature of from 10°C to 80°C, and thereafter cooling the slurry to a temperature of 15°C to 20°C. Thereafter carbon dioxide is introduced at a rate and under prescribed reaction parameters to produce basic calcium carbonate.
• BCC basic calcium carbonate
• PCC novel precipitated calcium carbonate
• AESD average equivalent spherical diameter
• large irregular shaped particles having an AESD of between about 15 and about 25 or more microns and large, rough-textured, multi-faceted spheroids having an AESD of between about 5 and about 15 microns.
• the precise size or shape of the particles can vary according to the parameters of the reaction, as a general proposition the process of this invention will result in particles which would be larger than would be obtainable by previously known processes.
• the process of this invention enables the preparation of "tailor-made" particles of shapes and sizes which can then be utilized for specifically selected applications.
• This invention also contemplates paper products or food products including PCC particles produced by the process of this invention.
• the PCC particles of this invention with an average equivalent spherical diameter (AESD) range of between 1.8 and 2.5 microns are particularly useful as fillers for high strength paper.
• Particles between about 2 and 5 microns are particularly useful as coatings for dull finish paper.
• the large size particles of this invention are useful in food applications. Other applications for these particles can be found in ceramics, paints, plastic, rubber and other composite materials.
• FIG. 1-3 are photomicrographs, taken at a magnification of 200OX, of PCC particles formed according to the process of this invention utilizing as an additive 0.3, 0.2 and 0.1 percent by weight of sodium hexametaphosphate (SHMP) , respectively.
• FIG. 4 is a photomicrograph, at the same magnification as FIG. 1 to which no phosphate has been added.
• FIGS. 5-6 are photomicrographs, also taken at a magnification of 2000X, of large size irregular shaped particles of PCC formed according to the process of this invention utilizing as an additive 0.5 and 1.0 percent by weight of SHMP, respectively.
• FIGS. 7-9 are photomicrographs, also taken at a magnification of 2000X, of PCC particles utilizing a different lime source than used in FIGS 1-3 but the same additive at the same level of concentrations respectively corresponding to FIGS. 1-3.
• FIGS. 10-13 are photomicrographs taken at a magnifi ⁇ cation of 2000X of PCC particles formed according to the process of this invention utilizing as an additive 0.25, 0.4, 1.0 and 1.0 percent by weight of SHMP, respectively, but at ranging temperatures of 15-20°C, 15-20°C, 35°C and 15-20°C, respectively.
• a.10 micron reference marker is indicated in each of the photomicrographs of FIGS. 1-13.
• the particles of PCC of a size generally larger and of a morphology different than heretofore known are provided by adding carbon dioxide to an aqueous slurry of BCC which has been preformed, or formed in situ, under a selectively controlled reaction environment.
• the process of this invention provides the aforesaid particles having an average equivalent spherical diameter (AESD) of from about 1.5 to about 25 microns, by adding carbon dioxide to an aqueous slurry of BCC at an effective temperature of between 0°C and 60°C in the presence of an effective amount of surface active polyphosphate, said effective amount being between about 0.1 and 1.0 percent by weight of the slurry, the size and morphology of the particles being varied by the temperatures and amounts of polyphosphate employed. Above about 1% the polyphosphate rapidly begins to lose its effect on increasing size and at about 1.5% begins to show a reversal of the effect.
• AESD average equivalent spherical diameter
• the characteristics of lime may vary according to source. As will be explained hereinafter, this variance may sometimes impact upon the size of the particles; however, as a general proposition the particles, using the process of this invention, will be larger in size than would result from processes for the preparation of PCC heretofore known irrespective of the source of lime employed.
• the amount of polyphosphate additive needed to produce certain desired sized particles of PCC may vary because of the lime employed, but will generally be within the ranges specified.
• the concentration of polyphosphate should range within about 0.1 and about 0.4 percent by weight.
• the amount of polyphosphate needed to effect the desired discrete particle size can be in the upper or lower part of the range or slightly outside of the indicated ranges.
• a 0.1 percent polyphosphate content could produce discrete particles having an AESD of about 1.5-2.0 microns, while another source of lime might require a 0.2 or 0.3 percent or more polyphosphate content in order to effect the same particle sizes.
• the temperature of the reaction environment may similarly have an effect on the amount of additive required.
• temperatures in the lower ranges e.g. on the order of O°-20°C would produce smaller particle sizes than temperatures in the upper ranges, and would also necessitate higher concentrations of polyphosphate, i.e. in the 0.3-0.4 percent range, to effect the preparation of the desired larger particles.
• higher reaction temperatures will result in larger AESD micron sizes with concomitant smaller concentrations of polyphosphate.
• the discrete PCC particles having the aforesaid AESD of 1.5 to 6.5 microns and a generally prismatic shape it is preferable to operate the reaction at a temperature of between 15°C and 35°C and to employ the polyphosphate additive at a concentration of between 0.2 and 0.4 percent by weight.
• the discrete particles can be flocculated, i.e. they will be weakly bonded together.
• the morphological designation "prismatic" is used to define these particles, at least some of these particles could be said to be rhombohedral in shape.
• the concentration of polyphosphate employed as an additive to the BCC slurry should range between about 0.5 and 1.0 percent by weight, and the temperature range of the reaction environment should be between about 20°C to 60°C. Again, however, the temperatures can be empirically determined.
• the concentration of polyphosphate employed as an additive to the reaction environment should also range between about 0.5 and 1.0 percent by weight.
• the temperature of the reaction environment should be between 0°C and about 20°C and preferably between about 10°C and about 20°C. It should be noted that the rough-textured, multi- faceted large spheroids and the large irregularly shaped particles and composed of intimately fused crystals rather than, for example, agglomerates of individual nodules.
• the size of the other large particles of this invention defined above can also be affected by the source of the lime employed in forming the BCC slurry.
• BCC can be prepared by the aforesaid known processes, but preferably is formed by the partial carbonation of calcium hydroxide utilizing temperatures on the order of 0 to 20°C, with a range of between 10 and 15°C being preferred. It is also preferred that the controlled addition of carbon dioxide to the slaked lime slurry be carried out at a flow level of about 0.1 to 0.4 liters per minute per 100 grams of calcium hydroxide until about 60 to 70 percent of the slaked time has been carbonated.
• the surface active polyphosphates employed in the instant process are surfactants commonly used as scale inhibitants, sequestrants, deflocculants and detergent promoters. Any water-soluble polyphosphate of the formula
• M ( n+2 ) p _°( 3n - ⁇ -i) or ( MP0 3) n wherein M is hydrogen, ammonium or alkali metal and n is an integer of 2 or greater, can be used.
• Such polyphosphate in which an alkaline earth metal or zinc is the cation may also be used.
• Particularly suitable polyphosphates include the alkali metal polyphosphates and metaphosphates wherein n is from 2 to 25.
• alkali metal pyrophosphate tripolyphosphate and especially sodium hexametaphosphate.
• the carbonation of the BCC is continued until the product formation is complete and BCC is converted to the desired PCC end product. It is preferable that this conversion be completed at a pH of between 7 to about 8.
• Carbonation is usually completed in less than 1 hour and preferably between 15 and 30 minutes.
• the nature of the carbon dioxide gas for the carbonation is not narrowly critical; the standard mixtures of carbon dioxide in either nitrogen or air commonly used for such carbonation being satisfactory.
• the nature of the source for the starting lime to form BCC is not narrowly critical.
• either lime or hydrated calcium hydroxide may be used.
• the source of the starting lime may affect the amounts of polyphosphate or the temperatures to be utilized.
• EXAMPLE 1 A 4-liter jacketed, baffled, cylindrical stainless steel reactor, having an internal diameter of 13.5 cm, a height of 38 cm and a hemispherical bottom, equipped with a high-speed agitator having two, 5-cm diameter flat blade turbine impellers, positioned about 1.5 cm and 5.5 cm from the bottom and driven by a 1/15 hp variable speed motor, and a 0.3 cm, inside diameter, stainless steel tube curved under the center of the bottom blade for the introduction of a carbon dioxide/air stream, was used for preparation and reaction of BCC to form PCC.
• a 16.5 weight percent aqueous calcium hydroxide slurry was prepared by adding 300 g of granular active lime obtained from Mississippi Lime Company quarried and calcined in St. Genevieve, Missouri, hereinafter referred to as "lime A", having an available calcium oxide content of about 93 or more weight percent as determined by ASTM procedure C-25-72, to 2100 g of water in the above-described reactor at about 50°C and stirred at 1000 rpm for 10 minutes.
• the slurry was diluted to about 12 weight percent, screened through 60 mesh to remove grit, and cooled in the reactor to 10-15°C.
• the agitator was adjusted to 1900 rpm and the slurry was carbonated to basic calcium carbonate (BCC) by introducing a gas mixture of 12 volume percent carbon dioxide in air at 1.67 standard liters per minute (SLM) into the slurry while holding the reaction temperature below 20°C by running iced cooling fluid through the jacket. The carbonation is continued until about 67% of the lime is carbonated, which signified the formation of BCC.
• BCC formed by the process is then either used immediately to produce precipitated calcium carbonate or filtered and dried for later use.
• EXAMPLE 2 A sample of 3000 ml of slurry containing 535 g of BCC in water having a pH of 12 made from lime A, and following the procedure of Example 1, was placed into the equipment described in Example 1. The temperature was adjusted to 25°C. A freshly made solution containing 1.2 g (0.3 weight %) of sodium hexametaphosphate (SHMP) (Hooker Chemical, Technical grade) in 50 g of water was added to the BCC slurry and stirred for 5 minutes at 1900 RPM. Stirring was continued during carbonation at 1.67 SLM using 12 volume percent C0 2 in air for about 40 minutes until the pH decreased from about 12 to 8 and remained stable, the latter indicating completion of carbonation. The temperature was allowed to rise to 35°C during carbonation.
• SHMP sodium hexametaphosphate
• a sample of the slurry was extracted for particle size analysis.
• the remaining slurry was passed through U.S. Standard .No. 325 (44 microns) sieve to remove grit and then vacuum filtered on a Buchner funnel.
• the filter cake was dried at 120°C for 16 hours to give a precipitated calcite product having a specific surface area (SSA) of 1.8 m 2 /g and an average equivalent spherical diameter (AESD) of 6.1 microns with 87 weight percent of the particles within ⁇ 50% of the AESD, i.e. from 9.0 to 3.0 microns.
• SSA specific surface area
• AESD average equivalent spherical diameter
• a photomicrograph of the product at 2000X is shown in Figure 1.
• the surface area of the product was obtained using a Micromeritics Flowcarb II 2300, which employs BET theory with nitrogen as the absorbing gas.
• the particle size was determined by a sedimentation technique using a Micromeritics Sedigraph Model 5100 on an aqueous dispersion of the product at about 3% and using about 0.1% carboxylated polyelectrolyte (Daxad 30) as a dispersant.
• EXAMPLE 3 Discrete precipitated calcium carbonate particles of varying sizes were prepared using the process described in Example 2 except decreasing levels of sodium hexametaphosphate were used to give products with decreasing particle sizes as indicated in the following table I as shown in 2 and 3.
• run 1 corresponds to fig. 1
• run 2 to fig. 2 run 3 to fig. 3.
• Run 4 is a control indicating the particle size in which no sodium hexametaphosphate is added. It is represented in Fig. 4.
• Precipitated calcium carbonate particles of a very large size were prepared using the process described in Example 2 except increasing levels of sodium hexameta ⁇ phosphate were used to give products with increasing particle sizes and a change in morphology to fused irregular particles as shown in the following table and in Figures 5 and 6.
• run 1 is the same as run 1 of Table I
• run 5 corresponds to Fig. 5
• run 6 correspond to Fig.- 6.
• EXAMPLE 5 Precipitated calcium carbonate of varying sizes was prepared using the process as described in Examples 2 and 3 except that a different lime source was used to prepare the BCC used in the synthesis of the products indicated in the following table.
• This lime source hereinafter referred to as "lime B”
• the concentration of the BCC was 486 grams in 3000 grams of water and was carbonated using 1.5 SLM of 28 volume percent CO- in air for about 30 minutes.
• the results indicated in Table III below indicate similar effects in size increase with increasing SHMP levels but to a different degree depending on the lime source. Runs 7, 8 and 9 in Table III correspond to Figs. 7, 8 and 9. Runs 4, 2 and 1 are repeated for contrast.
• EXAMPLE 6 Precipitated calcium carbonate was prepared using the process as described in Example 5, but the temperature was held at 20°C rather than from 25 to 35°C during carbonation. The results in the following table indicate that lower reaction temperatures give smaller particle sizes and that even at a higher level of SHMP the particles were significantly smaller and more spheroidal in shape. In Table IV, runs 10 and 12 were conducted at 15-20°C while runs 8, 9 and 12 were conducted at 25-35°C. Runs 10 through 13 correspond to FIGS. 10-13.
• EXAMPLE 7 A handsheet study was completed to compare standard calcium carbonate fillers (ground limestone, scalenohedral PCC) with a PCC of the present invention (prepared according to the procedure of Example 3) . Properties of the calcium carbonate fillers evaluated in this handsheet study are summarized in Table V below. Paper samples were prepared using a Formax (Noble and Wood-type) handsheet former. The fillers were added to a pulp blend consisting of 75% bleached hardwood kraft and 25% bleached softwood kraft beaten to a Canadian Standard Freeness of 400 and a pH of 7 to 8.
• EXAMPLE 8 The unique properties of the large prismatic calcite of the present invention as a dull finish paper coating pigment were shown by substituting it for a low gloss spherical calcite used for dull coatings on an equal weight basis in a standard low gloss paper coating formulation. The physical properties of the pigments are compared in Table VII. A typical paper coating formulation is indicated in table VIII.
• Styrene/butadiene rubber latex Dow 620, Dow Chemical Co., Midland, MI
• the coating colors were prepared by first slurrying the coating clay at 73 percent solids using 0.1 percent sodium polyacrylate dispersant, based on clay, using a Cowels-type mixer with a two-inch blade at 5000 RPM for 15 minutes.
• the calcium carbonate pigment was similarly slurried at the highest possible solids using a sodium polyacrylate dispersant as required by the pigment's dispersant demand.
• 50 parts of the calcium carbonate pigment slurry were added to 50 parts of the clay slurry (dry weight basis) with the mixer at approximately 1200 rpm.
• the latex, starch, lubricant and insolubilizer were then added, and the pH of the coating color was adjusted to between 8.5 and 9.0 with ammonium hydroxide. After mixing for approximately 5 minutes at 1200 RPM, the percent solids and viscosities of each coating color were evaluated as indicated in Table IX below.
• the pigment of the present invention produced better low shear and high shear viscosity than the spherical Calcite identified in Table VII.
• coated sheets were dried on a rotating drum at 100°C. All coated sheets were then conditioned for 24 hours at 23°C and 50 percent relative humidity. After conditioning, coated sheets chosen on the basis of nearly equivalent coat weight were supercalendered 3 nips on a laboratory supercalender opera ⁇ ted at 1600 pounds per linear inch with the rolls heated to 66°C. The coated sheets were then subjected to a series of tests listed in Table X below along with the results. TABLE X
• the excellent dulling properties of the large prismatic calcite of the present invention are evident.
• the pigment not only outperformed the spherical calcite- but did so while producing superior ink snap, a more ink receptive surface and better picking strength.

Landscapes

• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Inorganic Chemistry (AREA)
• Life Sciences & Earth Sciences (AREA)
• Geology (AREA)
• Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)
• Paper (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=24851978

Family Applications (1)

Country Status (5)

Cited By (4)

Families Citing this family (39)

Citations (5)

Family Cites Families (23)

• 1992
  • 1992-05-28 WO PCT/US1992/004202 patent/WO1992021613A1/en active Application Filing
  • 1992-05-28 AU AU21572/92A patent/AU2157292A/en not_active Abandoned
  • 1992-06-04 MX MX9202653A patent/MX9202653A/es not_active Application Discontinuation
  • 1992-06-08 TW TW081104451A patent/TW209207B/zh active
• 1995
  • 1995-06-08 US US08/487,766 patent/US5643415A/en not_active Expired - Fee Related
• 1997
  • 1997-08-28 US US08/919,247 patent/US6312659B1/en not_active Expired - Fee Related

Patent Citations (5)

Non-Patent Citations (2)

Also Published As

Similar Documents

Legal Events